Automatic transmissions are utilized in a number of applications, for example, in motor vehicles, to transmit the torque from the driving motor to an output. For example, the torque may be transmitted from an internal combustion engine to the wheels. The operation of the transmission permits the engine to operate in the most advantageous torque ranges. Depending upon the type of transmission, the torque transmission from the engine to the output may or may not be interrupted during the shift from one gear ratio to another. Today, in automatic transmissions wherein gear shift takes place "under load", that is without force or torque transmission interruption, the transmissions utilize planetary gears. To change the gear ratio, one of the gears, for example the sun gear or the planet gears is either driven or braked hydraulically by the activation of clutches or brakes. Valves are provided which control the amount of fluid in hydraulic units operating the gear elements associated with the individual gear ratios. During gear shift from an engaged or prior to a newly selected gear, the valve associated with the engaged, or prior, or old gear must be shut off while the valve associated with the newly selected or new gear i.e. the gear to be engaged must be activated. In order to prevent an interruption in torque transmission, the valve associated with the gear to be engaged must be activated before the valve associated with the engaged, or old gear is shut off. This process is known as positive overlap control. A transmission control arrangement of this type is described in German published application DE-OS 27 42 031 to which U.S. Pat. No. 4,228,700, ESPENSCHIED et al., corresponds.
The actual overlap operation of the friction elements of the transmission must be delayed relative to the time that a signal indicating a desired gear shift is received in order to be sure that the hydraulic units which operate the friction elements are completely filled. This increases the time required for a gear shift.
Further, when the hydraulic units are completely filled and the friction elements engage without transmitting any substantial torque, the latter are under an additional load and a sudden decrease occurs in the output torque.